Man.. No life drawing for way too long. Finally found a place to live. So even better things will begin very soon.
Mixing your strokes in Multiply and Colour Dodge modes give you completely different colour curves, so USE THEM.
If you want to get faster, do the best job you can, and take a long time on each piece. Speed comes from knowledge.
If you can help it, adjust your brush pressure to make the application of value resemble the application of actual light. Usually this involves softening the tip feel, because the value of your surface will be proportional to the cosine of the angle the light is hitting it at. see this. Roughly if the plane being hit by light perpendicularly is at value 10 (and the shadow is at value 0), at light angle of 60º relative to the surface plane the value will be around 8.6, at 45º it will be 7, at 30º it will be 5, at 15º it will be 2.6 and at 0º it will be 0.
Never settle for your first pass at a drawing or a concept, but it will always have some crucial elements that you have to catch and take with you into your next iterations.
Use pure black sparsely. Create atmosphere with almost black instead.
Have a lot of interesting things along the line of sight of your characters. Viewers' eye will always follow it.
Use the Histogram to check your values and make sure your picture is coming out in the key you intended.
When taking feedback, try to interpret what the person is saying and where they're coming from, instead of taking what they say at face value. Try your best to understand why you're getting such a response and what it really means, because words are never enough to communicate visual ideas. More often than not, the critique is hitting some crucial truth, but it's up to you to discover what that is.
Design and visual language mean completely new things to me now. The best designs use symbolic shapes and allude to various objects we see daily in order to elicit an emotional response, much like metaphors in writing. Except design is more like music, since the language of shapes is about as abstract as the language of notes (though much more complex).
You will always have a tougher time making things read in shadow, so make sure that in your compositions important shape-defining edges aren't in shadow. Makes sense, right?
To get unexpected colour schemes, you can't rely on your own knowledge of colour. So experiment with as many tricks as you can. Or do tons of weird colour studies.
Always know which hue you're going towards and max out saturation and value when laying down your painting fundament. You want as many hues and as much contrast as you can manage. You can always tone it all down later by colour picking and mixing edges.
MIX GOD-DAMN COMPLEMENTS, BATMAN! And saturate the shit out of them while you're at it.
Actually, mixing in small bits of complements makes your colours sparkle much more than picking the "right" colours. This is because your eyes are mixing the colour instead of photoshop.
Take colours that aren't working and shift them towards colours that are already on the canvas. As in, take a pink skin tone and put it on a green leather belt that's looking muddy. It will work, trust me.
You can extend your colour range by adding little accents of random saturated hues here and there, but ratios of all the hues in your colour gamut must be preserved.
Every colours fits! Because they all get mixed in the eyes anyway. Try to extract bright saturated tints from your boring paintings so that the eye could mix them and make your picture look more realistic.
Have as many hues on your canvas as you can! Push shit all the way around the colour wheel! You just need to blend them at the right spots.